Pneumatic tyres



NOV. 5, 1957 p. BOURBON 2,811,998

d Jan. 27, 195

, I/Il/I/m,

United States Patent 6 PNEUMATIC TYRES Pierre Marcel Bdurdon, Paris, France, assignor to Compagnie Generale des- Etablissementsl Michelin (Robert Cie), Clermont- Ferrand Enance This invention relates to pneumatic tyre covers and is concerned with a construction of tyre cover possessing good road grip and long wear properties.

The main object of the invention is an arrangement of the adjacent layers of the upper sheets of the tyre cover.

A further object is the combination of the adjacent layers of the upper sheets thus arranged in combination with a particular construction of the layers of the carcass in the side walls of the tyre cover.

Various proposals have already been made for the construction of the upper sheets of pneumatic tyre covers. Certain of these constructions are with the object of preventing puncturing of the tyre. They consist, for example, in arranging in the tread band or portion or underneath this band layers of flexible metallic fabric or narrow flexible metallic strips interlaced or not. These constructions have no effect on the road grip of the tyre because they render the upper sheets of the tyre indeformable under the action of the stresses set up in directions parallel to the rolling surface.

It has been proposed thus to combine, with a carcass, flexible wires arranged obliquely with respect to the circumferential direction of the tyre and which are fixed to the carcass of the coverinstead of to the edges of the tread band and on both sides of the latter. But this reinforcement is not indeformable under the action of the compression stresses parallel to the rolling surface since, under the influence of these stresses, various flexible wires can bend and do not offer therefore any resistance.

It has therefore been proposed to give the tread band a great resistance to the compression and traction stresses parallel to the tread band by arranging in this tread band layers described as triangulated layers, that is inextensible layers of wires embedded in the rubber, the wires in one layer being parallel to one another but arranged with the wires in different layersparallel to at least three different directions. This solution, which gives in practice excellent results, necessitates the use of at least three layers adjacent the upper sheets. The rigidity in the direction of resistance to the compression stresses parallel to the running surface is obtained by reason of the fact that the whole of the wires of the individual layers form indeformable triangles. But each layer by itself does not offer suflicient rigidity to certain compression stresses parallel to the rolling surfaces. For example, if these stresses are orientated in a direction which makes a small angle with the wires in that layer, these wires can be displaced and finally become slightly curved, in such a manner that the resistance in this direction of each of the layers is no longer ensured. Even an arrangement of two layers formed of inextensible wires embedded in the rubber does not permit of obtaining very great rigidity the compression stresses in all directions parallel to the rolling surface. Moreover it is possible for the wires of these two layers to have in relation to one another under the action of the compression stresses, scissor movements, by reason of the elasticity of the rubber.

2,811,998 Patented Nov. 5, 1957 Only; a combinationof three layers at least, formed of inextensiblewires embeddedin the rubber enabled the desired result to be'obt-ained heretofore.

According-to the present invention, resistance to compression stresses set up in any direction whatsoever parallel tot-he rolling surface is. obtainedby arranging'within this tread bandor in the immediate vicinity of the latter twolayers of restraining elements e. g., metallic cords; each being covered with a continuous layer of rubber havin'gaveryhigh modulus ofelasticity. In each l'aye'nthe cord elements}areparallel toone another; but the direction of the elements-is different in both layers.

B-y reason of the high modulous of elasticity of the covering rubber andi the adherence ofthese cord elements tothis rubber-wli-ich can be replaced; without'd'epartihg fromthe invention by wires, cords; or" strips, of a ma terial possessing a resistance to compression substantially equivalent to that of the metal cord elements-the rubber holds these cord elements as if in a sheath and prevents the separation of the wires, of which they are formed, as well as any relative scissor movements of the wires or cords. In consequence, there is obtained with two layers of metal wires or similar elements a very high resistance to the compression stresses in all directions parallel to the rolling surface, like that obtained in the tire disclosed in the United States Patent No. 2,493,614 with three layers of triangulated cables.

Preferably the modulus of elasticity of the rubber, in which the wires, cords, or strips are embedded, has a value greater than 350 (metric system) corresponding substantially to a Shore hardness greater than 72.

The invention comprises also a method of construction according to which the upper sheets, thus reinforced by a rigid core, which is flexible both in a transverse and radial direction, are combined with a carcass formed by one or more flexible layers of cords, parallel to one another and directed substantially according to the meridian of the tyre.

The inventor has found that this combination of the reinforcement in the upper sheets and the construction of carcass give particularly remarkable results. These are due mainly to the fact that the carcass, thus formed, does not exert on the reinforcement any sudden stresses during running, stresses which tend to give a distortion to the reinforcement of the upper sheets and, in consequence, nullify the eifect of transverse rigidity which it is proposed to obtain.

' The inventor has also found that the reinforcement constructed in accordance with any of the embodiments described above, should preferably be limited laterally in the vicinity of the edge of the tread portion and should not extend substantially beyond this edge in order not to interfere with the flexibility of the side walls.

The invention is illustrated in the accompanying drawings in which:

Figure 1 is a plan view with parts exposed, and,

Figure 2 is a transverse section of the upper sheets of a pneumatic tyre in accordance with the invention.

Figure 3 is a section of the tyre showing the upper sheets and the meridial cord elements of the carcass.

In the drawings 1 indicates a tread portion and 2 the carcass, 3 being the reinforcement of the carcass, formed of meridial cord elements (that is to say located in planes passing through the axis of the pneumatic tyre).

In Figures 1 and 2, there is shown a method of construction in which the reinforcement according to the invention, is formed of two layers each consisting of cord elements parallel to one another embedded in a layer of rubber having a high modulus elasticity and arranged in different direction in the two layers.

5 and 6 indicate the two layers, and 7 and 8 the cord elements respectively of the layers 5 and 6, 9 being the rubber having a high elasticity in which are embedded the cord elements.

' The'cornpression stresses parallel to the surfaceS cannot deform the arrangement of layers 5 and'6 whilst, the arrangement maintains suflicient flexibility with respect to forces in the direction of the arrows F or F What I claim is: r

l. A tire casing comprising a carcass having flexible rubber-containing side walls, a rubber-containing ground; contacting tread portion on the outer periphery oi said carcass, a pair of superposed, directly adjacent, substantially parallel reinforcing plies within said carcass and substantially coextensive with said tread portion each ply comprising a plurality of parallel metallic cords e bedded in a layer of rubber having a modulus of elasticity of at least 350 and a shore hardness greater than 72, said layer having a modulus of elasticity substantially higher than the other rubber in the side walls and tread portion EQMLQQB and the cords in one ply extending at an angle to the cords in the other ply and to the median plane of said carcass.

2. A tire casing as set forth in claim 1 in which the side walls include at least one ply of reinforcing threads, said threads lying substantially in the meridian plane of the carcass.

References Cited in the file of this patent 

